Hotchkiss evaluated the Colchester Combi 6000 from the Colchestersales (UK) Southern Technical Centre at RK International in Erith, Kent, to represent the best return on investment.
The Hotchkiss family has been associated with engineering since at least 1799 when John, a Royal Navy Lieutenant invented a mechanism for lifting heavy weights and ships anchors. Indeed, it was a modification of his development that is said to have helped the British fleet to outgun the opposition at the Battle of Trafalgar because it enabled cannon balls to be transported far quicker and easier to the gundecks. Today, the family owned Hotchkiss Group, located at West Kingsdown, a stones throw from the Brands Hatch race circuit in Kent, is a specialist heavy machine workshop and general engineering business.

The Group is split into two operations.

John Hotchkiss Engineering named after the current managing director Bill Hotchkiss' father, is still well known for developing, producing, re-engineering and refurbishing rolls largely for the paper industry but also applies its diverse skills to the cable making sector, mining, shipping, car breaking and food producers.

The heavy duty operations of the business would not normally be expected in the Kent countryside - perhaps more at home in the Midlands or North East, but the skills in the business are very specialised for the 23 people operation.

A further 40 are also employed 20 miles away in Strood at the Group's contract engineering operation, Westwell Developments, which undertakes refurbishment, rebuilding and resiting of plant and machinery.

These projects range from fragmentisers used in scrap metal reclamation weighting up to 40 tonnes each, to pump transmissions for a wide range of industries.

The nature of the business is obvious when viewing the West Kingsdown machine shop where craneage can manoeuvre rolls and fabrications weighing up to 60 tonnes.

Its largest lathe has 2.6 m swing by 11.2 m between centres, two other lathes have 12 m and 8.5 m between centre dimensions but by clever siting of beds these machines can form a single unit, with a massive 20 m between centres capacity.

A 17 m long roll grinder has a 1.6 m swing by 10 m between centres and a CNC mill a 6 m by 8 m table.

It was, however, the demand for higher precision and productivity on smaller shaft and chucking work for refurbishing and general turning that recently set Bill Hotchkiss's workshop team to look across the market for a CNC lathe to replace an ageing centre lathe.

They eventually evaluated the Colchester Combi 6000 from the Colchestersales (UK) Southern Technical Centre at RK International in Erith, Kent, to represent the best return on investment.

In particular, it was the machines credentials as a combination lathe able to perform one-off tasks, have very easy to use programming assist and its ability to faithfully reproduce further components when required under automatic cycle that scored highly in the evaluation.

Says Bill Hotchkiss: 'We are engineers and are constantly involved with quite complicated mechanisms and structures.

While we tend to 'engineer' solutions on a large scale, we require high levels of flexibility in our machining because we never know what is going to come through the door.

Our equipment has to be real work horses so top of the agenda for any lathe we were going to install was real fitness for purpose.' The Hotchkiss family definitely has engineering in the genes.

In 1872 Benjamin Berkley Hotchkiss, credited by Bill as probably the most famous of them all, invented the revolving-barrel machine gun and a magazine rifle that became widely used in British, French and American Military.

Later he turned his talents to designing engines, particularly the internal combustion engine, founded the company that produced the famous Hotchkiss car in 1903 and is now sought after by enthusiasts around the world.

In 1930 Donald Hotchkiss, a ship's architect invented the coned propeller used by tugboats for manoeuvring ships in harbour and Bill's father John, who started the current company in 1938 with just £75, invented the portable rotary lathe in the 50s.

His invention was a breakthrough because it enabled in-situ machining and repair work to be carried out on bearing journals on large rolls in paper mills for instance, saving the time and expense of major stripdowns.

He also developed an in-situ keyway cutter able to cut keys in shafts up to 75 cm long by 10 cm wide and another invention of his was the HB static-spindle bearing cartridge that totally revolutionised roll installation and maintenance.

His development enabled the bearing to be changed in-situ, without the roll having to be removed from the machine.

Other inventions include a single bearing 12 metre hydraulically driven floor level rotary turntable capable of coiling some 600 tonnes of submarine power and optical fibre cables without twist during manufacture.

Components machined today on the Combi 6000 are to far higher tolerance and surface finish than could be produced before and quite often repair and reclamation demands a lot of turning skill which, operator Dave Plant maintains, the Manual Guidei software on the Combi is extremely useful in support of what he needs to do.

He describes an often and classic case that would take ages to get the component running true and parallel when, say, a journal diameter has to be remachined.

'I set it true in a four-jaw chuck and then quickly program in a slight taper to compensate for parallelism rather than have to mess around jacking the tailstock.

This type of flexibility has allowed us to reduce a job that could take around three days to within a shift or at worst, a day and a half.' Much of the work is shaft based, these can be up to 300 mm diameter by 1,500 mm long and involving multi step diameters and the finish turning of journal diameters.

Tolerances tend to be 0.012 mm for bearing diameters and surface finish straight from the machine are often required to be within 0.8 and 1.6 um RA.

Says Dave Plant: 'Most of our shaft work is on pretty tough material such as EN24T and EN42 and due to the type of work a lot of threads are machined.

Here I find the screw cutting macros on the Combi are really helpful as we have to machine both metric and imperial and these can be between 50 mm and 300 mm diameter by 100 mm long.

We also have to produce the occasional taper thread.' He also makes use of the simulation on difficult parts and has found the rigidity of the Combi ideal for roughing out with 3 mm depth of cut on the shaft work.

'It will easily cut faster but you need to take into account insert life.

We are not a production shop,' he says, 'most parts are just single items but we do use the CNC for repeat cycles when we can have batches of up to six parts.' As Bill Hotchkiss maintains: 'We needed a machine that would give us a good quality turn.

It was the guys in the workshop that made the decision and they are the ones who make the installation a success.

When we look at the overall package from Colchestersales and the price that was paid, we feel we are getting a very good return on our investment.'